Seven people were killed and more than 20 were injured Saturday in the crash landing of a Russian airliner.

Russian airline UTAir, which owns the Tu-134 jet, has blamed heavy fog for the incident at the Samara city airport in southeastern Russia. But officials say they also are probing whether the crash landing could have been caused by a pilot error.

Preliminary investigations showed that the plane scraped the ground off the landing strip before it plowed through the runway and broke apart.

The plane carrying 50 passengers and seven crew was enroute from the Siberian city of Sorgut. Up to 30 passengers were not physically injured, but were treated for shock.

The airport at Samara said normal operations resumed later in the day.

Depending on its configuration, the Tupolev Tu-134 is capable of seating up to 96 people.

It was the standard short-haul jet airliner in the Soviet Union and eastern Europe for many years, but is now considered outdated.